To provide a semiconductor device manufacturing method and a semiconductor device, which can improve productivity without reduction in quality.

A present semiconductor device manufacturing method comprises: a modified region formation process of irradiating laser beams L in a thickness direction of a semiconductor substrate 10 by fixing a focal point P of the laser beams L at any one point inside the semiconductor substrate 10 to successively grow a modified region K; an etching process of removing the reformed region K only by etching the semiconductor substrate 10 which has been subjected to the modified layer formation process from one surface 10a side to form a through hole 14 or a recess 16 in the semiconductor substrate 10 thereby to manufacture the semiconductor device.